1. Field of the Invention
The present invention relates to a light-beam deflecting device with a photonic crystal, an optical switch using the same, and a method of deflecting a light beam with a controlled angle by use of the photonic crystal.
2. Disclosure of the Prior Art
Photonic crystal is of a multi-dimensional periodic structure obtained by periodically arranging at least two materials having different dielectric constants at an interval substantially equal to a wavelength of light. In the expectation that the photonic crystal would remarkably enhance the control of light, it is being vigorously developed as optical devices of the next generation.
For example, an optical switch with a photonic crystal 1xe2x80x2 having a two-dimensional periodic structure is disclosed in Japanese Patent Early Publication [kokai] No. 10-90634. As shown in FIG. 17, this optical switch is for switching between the ON position (transmission) where a light beam incident on the photonic crystal (=incident light beam) is allowed to pass through the photonic crystal, and the OFF position (reflection) wherein the incident light beam is reflected from the photonic crystal to prevent the transmission of the incident light beam.
That is, light beams provided from a pair of optical fibers 12a, 12b are incident on the photonic crystal 1xe2x80x2 through collimator lenses 14a, 14b and polarizers 15a, 15b. The optical switch comprises a means for irradiating a control light 21 to the photonic crystal 1xe2x80x2 through a circular polarizer 22. The irradiation of the control light 21 causes a change in a photonic band gap (PGB) structure of the photonic crystal 1xe2x80x2, so that it becomes possible to switch between the ON and OFF positions. In the ON position, the transmitted light beam passing through the photonic crystal 1xe2x80x2 is output through a pair of polarizers 16a, 16b. 
However, since the purpose of the above optical switch is to switch between the ON position for allowing the incident light beam to pass through the photonic crystal and the OFF position for reflecting the incident light beam from the photonic crystal, this optical switch merely provides the presence or absence of the transmitted light beam as the output. This becomes to narrow application areas of the optical switch.
On the other hand, if a direction of the transmitted light beam provided from the photonic crystal can be controlled by deflecting the light beam incident on the photonic crystal, it is expected to provide a new optical switch using the photonic crystal, which comprises an optical input terminal for receiving the light beam incident on the photonic crystal and plural optical output terminals each having the capability of providing the transmitted light beam from the photonic crystal. That is, according to such a new optical switch, since the transmitted light beam can be provided from a desired one of the optical output terminals by controlling the deflection of the incident light beam, this kind of optical switch will find widespread application.
Therefore, a primary concern of the present invention is to provide a compact light-beam deflecting device with a photonic crystal, which has the capability of deflecting a light beam incident on a side of the photonic crystal by a controlled angle to output a transmitted light beam having a desired direction from the other side of the photonic crystal.
That is, this light-beam deflecting device comprises a photonic crystal designed to have a photonic band gap wavelength that is different from a wavelength of a light beam to be incident on the photonic crystal, and a deflection controller for applying an amount of energy to the photonic crystal to deflect the light beam incident on an incident side of the photonic crystal, and provide the transmitted light beam, which forms a desired angle with respect to the light beam, from a side other than the incident side of the photonic crystal.
It is preferred that the photonic crystal comprises at least two materials having different refractive indexes, and the deflection controller controls a ratio of refractive index between those materials by applying the energy to the photonic crystal.
When at least one of the materials of the photonic crystal is an electro-optic material, it is preferred that the deflection controller applies an electric field to the photonic crystal as the energy. In this case, no mechanical external force is applied to the photonic crystal as the energy. Therefore, the light-beam deflecting device is allowed to stably operate for an extended time period with a high degree of reliability. In addition, since the deflection controller electrically controls electric field strength applied to the photonic crystal to change the deflection angle of the incident light beam, it is possible to provide the compact light-beam deflection device having a quick responsivity.
Another concern of the present invention is to provide a new optical switch using the above-described light-beam deflection device, which presents advantages of preventing cross talk of optical signals and ensuring a high transmitting efficiency.
That is, this optical switch comprises the light-beam deflection device of the present invention, an optical input terminal provided at the incident side of the photonic crystal, through which the photonic crystal receives the light-beam (=incident light beam); and a plurality of optical output terminals provided at the side other than the incident side of the photonic crystal, from which said transmitted light beam is selectively output.
More specifically, the new optical switch of the present invention comprises the above light-beam deflecting device, an optical input terminal provided at the incident side of the photonic crystal, through which the photonic crystal receives the incident light beam; and at least two optical output terminals. The optical output terminals includes a first optical output terminal provided at a side other than the incident side of the photonic crystal to output a first transmitted light beam passing through the photonic crystal, and a second optical output terminal provided at a side other than the incident side of the photonic crystal to output a second transmitted light beam, which forms a desired angle with respect to the incident light beam, and has a different direction from the first transmitted light beam.
A further concern of the present invention is to provide a method of deflecting a light beam incident on a side of the photonic crystal by a controlled angle to output a transmitted light beam having a desired direction from the other side of the photonic crystal.
That is, this method comprises the steps of providing a light beam having a wavelength other than a photonic band gap wavelength of the photonic crystal on a side of the photonic crystal, and deflecting the light beam incident on the side of the photonic crystal by applying an amount of energy to the photonic crystal to provide a transmitted light beam, which forms a desired angle with respect to the light beam, from the other side of the photonic crystal.
These and still other objects and advantages of the present invention will become more apparent from preferred embodiments of the present invention explained in detail below, referring to the attached drawings.
The present disclosure relates to subject matter contained in Japanese Patent application No. 2001-82863, filed on Mar. 22, 2001, the disclosure of which is expressly incorporated herein by reference in its entirety.